Hongzhou Lian

Eu2 + -Doped High-Temperature Phase Ca3SiO4Cl2 A Yellowish Orange Phosphor for White Light-Emitting Diodes

In this paper, we synthesized a novel yellowish orange phosphor, Eu 2 + -doped high-temperature phase (HTP) Ca 3 SiO 4 Cl 2 at 1020°C. The primary crystal structure of HTP-Ca 3 SiO 4 Cl 2 is determined as monoclinic structure with a space group of 14 P21/c. The excitation spectrum of Eu 2 + -doped HTP-Ca 3 SiO 4 Cl 2 exhibits a broad-band between 250 and 500 nm with three peaks of around 327, 371, and 426 nm, which are coupled well with the near-UV (n-UV) or deep blue emission of GaN-based light-emitting diodes (LEDs). Its emission spectrum shows a single intense broad emission band centered at 572 nm. The measured chromaticity of yellowish orange luminescence is x = 0.52, y = 0.45. Eu 2 + -doped HTP-Ca 3 SiO 4 Cl 2 would be suitable for yellowish orange phosphor of white LED because HTP-Ca 3 SiO 4 Cl 2 :Eu 2 + is excellent in the excitation spectral profile and the chromaticity.

Surprising arching sheet-like dendrites growing from BaF2 nanocubes

BaF2 nanocubes were prepared from quaternary reverse micelles of cetyl trimethyl ammonium bromide (CTAB), n-butanol, n-octane, and water. Interestingly, there are arching sheet-like dendrites growing between two neighbouring sides of these cubes. X-ray powder diffraction (XRD) analysis showed that the products were BaF2 single phase. Scanning electron microscopy (SEM) or transition electron microscopy (TEM) was used to estimate the size of the final products. The results showed that the shape and size of particles were strongly dependent on the reaction conditions, such as the temperature and reaction time. When the reaction temperature was 25 °C, we obtained cuboid-like particles with clean surfaces (no dendrites growing on them), and when the temperature was 35 °C, we obtained nanocubes with dendrites growing from them between the neighbouring sides. The influence of reaction time at a temperature of 35 °C is also discussed.

Synthesis and Fluorescence Properties of Eu2+-Doped KMgF3 Nanoparticles

The phase diagram of a cetyltrimethyl ammonium bromide( CTAB)/n-butanol/n-octane/KNO3-Mg( NO3)(2) system was drawn. Nanoparticles of Eu2+-doped KMgF3 were prepared from the quaternary microemulsions of cetyltrimethyl ammonium bromide(CTAB), n-butanol, n-octane and water. The X-ray diffraction(XRD) patterns were indexed to a pure KMgF3 cubic phase. The environmental scanning electron microscopic (ESEM) images show the presence of spherical Eu2+-doped KMgF3 nanoparticles with a diameter of ca. 20 nm. The emission of KMgF3: Eu2+ nanoparticles peaks at 360 mn. The excitation band was observed at 250 nm with a blue shift of ca. 70 nm compared with that of KMgF3: Eu2+ single crystal. The preparation method of nano-KMgF3: Eu2+/PMMA composite films was inquired into.